Charles Dharapak/AP Photo

Obama campaign manager Jim Messina put his spin on the South Carolina primary results this morning, calling Mitt Romney's loss there a "strong rebuff to what he calls his chief qualification for office."

Messina, citing an array of exit poll data in a memo to reporters, underscored the erosion of support for Romney among Republican primary voters and independents who said their top priority is the economy, despite the former governor's much-touted business experience.

"Romney is now 0-for-3 among independents," Messina said, noting Romney's loss of the independent vote in each of the three early primary states.

"But South Carolina's rejection stands out: it was the first vote in a state where the unemployment rate is higher than the national average, but voters rejected Romney's profit-at-any-cost record of cutting jobs, wages and benefits while making millions for himself and his Wall Street partners," Messina wrote.

While Romney's performance among independents in a primary is not necessarily indicative of how he'd do in a match-up with Obama, Democrats aren't taking any chances and plan to continue focusing their offensive against the man they see as the most formidable challenger to the president.

The Obama campaign's focus on Romney - even when former House Speaker Newt Gingrich has more delegates, not to mention momentum and sizzle -accentuates the political fears the Obama campaign has of him.

As the focus turns to Florida, the Obama campaign will open a new phase of attacks on Romney's record at Bain Capital and advance a narrative that he is out of touch and insensitive to the needs of the middle class citing his positions on mortgage relief, Medicare, and immigration reform.

Romney's release of his tax returns Tuesday will also be a focal point for Democrats to continue to make their case.

"In the last two weeks, he's changed his position from claiming that the law didn't require him to release them, to saying he 'maybe' will release them in April, and now to releasing just one full year of returns.  What is he hiding?" Messina said.

"This week Florida's voters will meet a candidate with no core values who believes he's entitled to play by a different set of rules. Like their predecessors in the other early states, they will see a career politician willing to say and stand for anything to get elected and is out of touch with working and middle-class Americans."

"Mitt Romney prides himself on being a great businessman," he said. "But the American people aren't buying what he's selling."

Romney campaign spokeswoman Andrea Saul told ABC News the Obama Team assault on the former Massachusetts governor is part of a "strategy to 'kill Romney,' the same way they engaged in a campaign of personal destruction against Hillary Clinton" four years ago.

"President Obama has presided over an unprecedented 35 straight months of 8 percent or higher unemployment, so it's no wonder his campaign is desperate to distract from his failed economic record," Saul said. "Rather than focusing on job creation and helping the middle class, President Obama and his campaign are focused on attacking Mitt Romney."